RICH

The RICH detector is a device for e+/e- identification in hadron and heavy ion induced nuclear reactions investigated with the e+e- pair spectrometer HADES. In the GSI energy regime (E/A=2AGeV) electrons and positrons emitted in nuclear collisions have velocities ß=v/c~1, while all hadrons have ß < 0,95. The Cherenkov effect can be used to discriminate electrons from hadrons and to obtain a trigger signal for events containing e+e- pairs. For a radiator with proper index of refraction the detector is even hadron blind and the Cherenkov opening angle is constant for leptons of nearly all momenta. The Ring Imaging Cherenkov (RICH) technique is the most appropriate solution for this problem.